Charging an EV that's stopped by the side of road Page 1 / 2

trade4us2, Sep 10, 3:04pm
Now read this carefully!
How much power does an EV need to charge it so that it can be driven for a short distance? I have a 1500 watt 230 volt power supply in the boot of my car.
I have watched a Youtube where they drove half a dozen EVs until their batteries were flat. (That was around 200 miles upwards.) Some of the cars could not be pushed even a few metres. In the test they did have a large diesel generator.
For several reasons I have a 230v power supply in my car. Is it worth trying to charge the EV at all, or just get a tow truck?

saki, Sep 10, 3:25pm
tow truck.

trade4us2, Sep 10, 3:50pm
Most EVs cannot be towed without damaging the motors.
I often help to get someone's car going. I also need to use an angle grinder or Skilsaw in remote places.

trade4us2, Sep 10, 4:14pm
I can run much of my house for 3 hours using the inverter in my car, or longer if I start the engine.
But I am not sure whether an EV could charge at only 1500 watts.

kazbanz, Sep 10, 4:35pm
An EV can be towed. With front wheels in the air of course.
IRONY would be a recovery vehicle with a HUGE smoke belching diesel genny powering up the charger for the "eco friendly" battery car.

tweake, Sep 10, 4:42pm
you would have to check if you can limit the rate of charge. the car may put to much load on the genny and the voltage drop could cause the charger to stop.

if you had a suitable genny (ie 2.4kw) then its just a matter of time and how much fuel you can carry.
plus it also depends on what you call a "short distance" and if you have to climb any hills.

s_nz, Sep 10, 5:05pm
First thing to be aware of is that EV's are check the likes of the earth connection prior to charging (in order to be safely changed outside with cables that might damaged from be run over etc). This means getting EV's can sometimes refuse to run off portable power supplies like generators (unless the test is spoofed with a neutral earth bridge - defeats some safety features)

Second issue is getting the EV to charge slow enough. Most EV's are capable of charging as slow as 6Amps 230v (1,380W if power factor is one). Some EV's (tesla) let you dial up the charging speed in small steps on the dash. Others (i3, Kona etc) let you choose in 3 course steps. For my it was 10A, 7.5A, or 6A using the portable cord. I think the NZ New ones are different. For the likes of the Nissan Leaf I don't think the power level can be picked in car at all, it will simply draw as much as it can up to the limit signaled from the EVSE (charge box). In this kind of EV, you would need to source a EVSE with a 6A max, or one that you can select the charge current.

Third issue is going to be speed. At 6A, using a nissan leaf, it will take a full hour to add 6.5km range. Will be a long wait.

Final issue is the capacity of your power supply. All good if it is a petrol generator and you have a few liters of fuel. If you are running an inverter from another cars battery, few cars alternators will make 1.4kW after overheads at idle (or even at speed), so the start battery will quickly be drawn down until the inverter cuts out on low voltage. If one of those AC powerbanks like the linked below, despite being $3600, and 21kG's, it will be flat in just under 1 hour (considering inverter losses).

In summary, as long as you can get the charge speed low enough, feel free to try out your charging solution, everything (other than the earth-neutral bridge) is faily safe to try.

Your position is unusual as you already carry the power supply, but for most people it is not worth the cost, weight or space of carrying it. EV's can be pushed, winched onto tow trucks etc if flat. There are lots of accounts of people flat towing powered on EV's too (can even re-gen power, but don't do it too long as it might overheat). Look up what happens with your EV when it gets close to flat. Most will have several warning's, and a turtle mode before they die giving more opportunity to stop safety compared to running out of petrol.

If this really concerns you, there are plug in hybrid options like the Holden Volt, BMW i3 Rex and Outlander PHEV that you could consider.

bigfatmat1, Sep 10, 5:15pm
Does it go into drive at all?
What sort of ev?
No you will not be able to use 1500w powersupply.
If you tow it chances are you'll blow the drain resistor in the pdm.

intrade, Sep 10, 5:45pm
i got a dometic 1600watt power supply i just used my 2hp onhanglow supercheap compressor on it i am going to experiment with my power supply in my house in taumarunui as its a switchover unit running my coffee machine in the morning on battery till 9 am when power drops in price . may have to start a business if it works well and get the whole lines company district on one of them . how to charge a battery on night power is the next task to figure out.
trade4us2 what one do you have i was getting it for that and for in the car to run power tools mobile like that aircompressor.

marte, Sep 10, 6:18pm
I think that I read carefully that the OP has a 1500 watt Power supply.
Not a generator of any sort.

No, a 1500 watt Power supply won't do the job unless it's got huge back up battery's & it's going to take hours to build up a charge in the EV.

Start - 240 volt wall output - reserve battery charger - reserve battery - invertor back to 240 volts - EV charger - several hours - EV's battery - EV electrics - EVs motor - Go.

gpg58, Sep 10, 6:40pm
s_nz wrote:
If one of those AC powerbanks like the linked below, despite being $3600, and 21kG's, it will be flat in just under 1 hour (considering inverter losses). In summary, as long as you can get the charge speed low enough, feel free to try out your charging solution, everything (other than the earth-neutral bridge) is fairly safe to try.
Link was not working for me, was that the yeti li 1400 power station?
Found specs elsewhere if so, also out of stock, but same price but came with a 100w panel.
Its only a tiny 1.425 kwh Li-ion NMC battery, and then as mentioned, take away inverter losses, so you sure would not get far charging with this useless item. (10.8 v 132 ah) and its only rated for 500 cycles as well, at $3600, they is totally dreaming, could easily get 2 x 260 ah's (6.2kwh) lifepo4's(claimed 6000 cycles) and a big inverter and have lots of dollars left over.

I am going to see which batteries last longest in my use(or work out better value), i have the lifepo4 310ah, and 3 x 335ah nomad ultra agm's, and 8 x 6v 210ah wet cells, all bought around the same time.

gazzat22, Sep 10, 8:54pm
Brother you got that right,just dont let the Green Eco Warriors know.Mind you they would just look the other way like their CO-Leader did with the "Green" school! Who said Electric Cars are the Future?

apollo11, Sep 10, 9:03pm
I think the car makers did when they started pouring investment into it.

pdc1, Sep 11, 7:42am
Just trying to understand why you can’t tow a EV. I would have thought it would have been just like driving downhill.
Is it because the vehicle has shut down from discharged batteries, or is it at anytime that they can’t be towed?
(I see that #9 has mentioned about the drain resistor in the pdm being damaged, whatever that means)

fishb8, Sep 11, 9:46am
Does towing it backwards charge up the battery?

s_nz, Sep 11, 10:05am
There are lots of examples of people rope towing EV's and having success. Generally they start the car up and have it in drive, so all the normal systems are working, and as you say, it is just like driving down an (epically large) hill. One issue that could be run into is that the "downhill" duration could be a lot more than the car was designed for, leading to stuff overheating.

I guess the recommendation against flat towin in many EV's is due to the risk that something potentially could go wrong. For example one could put a nissan leaf in "neutral" and then tow the car turned off. The nissan leaf dosn't actually have the ability to go in neutral, so if the wheels are turning the motor is turning. If the car is off, the cooling system is off, and the drive system is not working to manage voltages generated by the turning motor. Could easily electrically fry, or overheat something.

Obviously towing an illegally parked vehicle, or one that is broken down, it is unlikely the drive system can be powered up, so the wheels need to be lifted from the ground.

thepiercedkiwi, Sep 11, 10:07am
This is why our towing business has skates to go on the wheels

s_nz, Sep 11, 10:08am
Yeah, the goal zero yeti Li1400. Had an extra dot in the link, below one should work. Obviously you pay a premium for the the battery, inverter, display, charger, USB ports etc to be integrated into a single unit as opposed to building it up yourself. That said, there arn't many options for 230v units, hence why I picked this one.
They also have a 3kWh version for NZD $6k (out of stock), but that's 31kg.

I'm interested what you are using your power supply for. The three 335ah nomad ultra agm's you list above weigh 70.5kg each, so are pushing the limits of portability.

In my experience most EV owners don't carry additional batteries on bored, instead opting to stop a charger if they don't have enough range to make their trip in one. Same as the majority of petrol or diesel car owners who don't carry extra fuel in case the run out (and monitor the fuel gauge to avoid running out).

Even if you did have an epic amount of battery capacity, it is still going to take a long time to put into the car if you are restricted to 1500W. Sitting on the side of the road for three hours would only net you 15km more range. If that is what you need, calling a tow truck to take the car home or to a 50kW fast charger sounds like a more time effective solution. Unless you have other need for a massive powerbank, it would be a lot cheaper too.

We have a lot of fast chargers in NZ now, and electric cars like the Kona have 400-450km or real world range, so there isn't generally much need for portable roadside charging.
Interesting to note that the AA has launched it's first battery service van that includes EV charging in wellington. In addition to resolving start battery issues in petrol & diesel cars, it can provide 10km of additional range to an EV in 25mins. Not sure of the tech behind this, but would be useful for people caught just a few km from home or a fast charger. Flat EV callouts in the rest of the country are resolved via a tow truck. (Should note that they only get 70 such callouts a year from the 15,800 pure electric vehicles in the NZ fleet, so not super common).

harm_less, Sep 11, 3:15pm
No more irony than when you have to beat the feet to the nearest dino juice station when your suck, squeeze, bang, blow machine runs out of fuel.

bryshaw, Sep 11, 3:32pm
National will let you use bus lanes. Plenty of room if you break down.

headcat, Sep 11, 3:58pm
How then, do they get down hills? Mine will regenerate quite a few ks on a longish downhill stretch of road. how is this different from being towed? Now donning my asbestos suit.

apollo11, Sep 11, 4:43pm
Might be something to do with how the motors are geared down.

marte, Sep 11, 7:08pm
If it's being towed, the car could recharge only while the trucks slowing down or braking & that would regain energy that would normally be lost to the brake pads of the truck.

I read somewhere that they actually do 'Tow & charge up' a electric car in this flat battery situation. It gets a small charge up by the time it gets to the tow yard or garage, then it gets fully charged there afterwards. But it saves some charging time.

And then I read that they, Tesla, put the whole car on skids & slide it onto a specifically designed Tesla tow truck.
And that you can't tow charge other brands. Dunno who or what to believe now.

marte, Sep 11, 8:39pm
Can you recharge one EV off another's battery?

trade4us2, Sep 11, 11:27pm
When I am trying to charge an EV I can start the engine. It's a V8 with a large battery and generator. And I just want to charge the EV a little bit, to get it to a safe position.

Share this thread

Buy me a coffee :)Buy me a coffee :)